Self-acting breech bolt blocking device



Aug. 26, 1952 B. GUISASOLA 2,608,136

SELF-ACTING BREECH BOLT BLOCKING DEVICE Filed May 12, 1948 If f IO 9 uo 2* k INVENTOR. 6

5 BONIFACIO GUISASOLA Patented Aug. 26, 1952 SELF-ACTING BREECH BoLr Brooms DEVICE' S Bonifacio Guisascla, Eibar, Spain 7 U Application May 12, 1948; Serial No; 26,615

1 Claim. (c1. 89 190).

The present invention refers to a mechanism which automatically block's thebreechbolt of sub-machine guns and similar weapons when not actually action, thus, eliminating the risks of accidental firing of the weapon due to sudden movements or shocks, but which, nevertheless,

will not hinder or influence in any way the normal functioning of the gun to which it has been fitted.

In view of numerous accidents occasioned by thefuse of sub-machine guns and other automatic weapons of a similar type, the need for a safety unit that will securely block'the breech bolt when the weapon is not in use, has been felt for some time, since due to the mass of the bolt, any slight shock, such as may be experienced in jumping down from a vehicle or resting the weapon carelessly on the ground, will often provoke an accidental and dangerous explosion.

Up to the present, no satisfactory solution to this diniculty has yet been advanced and I therefore, submit the present invention which solves the problem definitely and perfectly, as it will be appreciated from the general and detailed description which follows.

Substantially, the invention consists of an angular rocking lever which can oscillate around an 7 axis inside the handle of the bolt, having a blocking claw at one end, and at the other a nicked button and a pin with a low pressure spring with a permanent tendency to introduce the blocking claw into the groove machined on the front face of the bore in which the breech bolt is lodged.

' Although this invention is extremely simple and on that account highly efficient, it will be more easily understood when taken in consideration with relation to the attached drawings, which illustrate a preferred manner of putting the invention into practice, and ar submitted by way of example not limitative as to details of form, saving the essence of the invention itself. The said drawings represent:

' 1 Figure 1, a vertical longitudinal section through the rear part of a sub-machine gun breech bolt and the lower part of its housing, showing the mechanism actually blocking the bolt (here deemed'to have reached the end of its forward stroke) against all further movement;

Figure 2, a partial and plan section of the blocking tip in its groove;

Figure 3, a similar section to Figure l, but at the very same instant in which the mechanism has, released (or is about to block) the bolt;

Figure 4, similar to Figures 1 and 3, but with the mechanism in place during the forward and rear movements of the bolt, that is to say, and in an intermediate position.

Figure 5, an enlarged detail of the rocking lever of Fig. 1, partly insection.

The reference numbers of all figures refer to same pieces or parts and indicate: I the angular or double winged rocker lever; l the blocking claw;2 the axis; 3 the pin and A the spring lodged inside the rocker lever; 5.the knurled knob; 6 the handle or pullerof the bolt .1, which moves longitudinally to and fro inside the housing 8, fitted with a stop groove 9 to engage the claw I on reaching the breech bolt in its foremost position, and the longitudinal slot l0 which guides th puller while the bolt is'moving.

The self-acting blocking unit in accordance with the invention, works in the following manner: To simplify this explanation, we assume the breech bolt blocked at the end of its forward stroke and, therefore, the recuperating spring nearly fully distended and the blocking claw I engaging the stop groove 9, thus preventing the breech bolt 1 from any further movement (see Figure 1). In order to prime the weapon, the bolt must be pulled back, which is done by crooking the forefinger around the puller 6, touching simultaneously and instinctively the knurled button 5 with the thumb and pressing it against the rear face of the puller, thus causing the rocking lever I to oscillate around the axis 2, whereby the other extremity of this lever, formed with the blocking claw l is disengaged from the stop groove 9, and the bolt l recoils until it is caught by the retention catch. The recovery spring is now tense and the weapon ready to be fired by passing the trigger (not represented). When the trigger has been released, the bolt advances again and the ordinary process of introducing a new cartridge into the breech chamber, percussion, explosion and the recoil of the bolt, with the subsequent recovery of force for the automatism of the weapon, is performed. The whole process requires such a short space of time, that the rock lever I, which during the shock produced at the end of the firing sequence and due to the distribution of volume with respect to axis 2, had turned on this same axis in such a manner that claw I had been disengaged from groove 9, has not time enough to reach groove 9 again, and the bolt 1 recoils as if the breech locking device were inexistent.

During the forward and recoil strokes of the bolt l, the upper surface of the laterally projecting parts of the blocking claw l originates a Slight ction at X on the bolt housing 8 (see Figure 4) due to the feeble pressure of the spring buffer 3 and d which always thrusts in the same direction. Once the bolt 1 is blocked, it can make loFFIcE;

- 3 no further movement without the express determination of the user, and it is therefore absolutely impossible for accidental or blind explosions to occur in arms fitted with the self-acting blocking device of the present invention.

Due to the particular form and disposition of all parts of this ingenious device, the ,breech bolt is automatically blocked whenever it'is desired to cease firing"; besidesg'it'has no infiuenc'e'whatsoever upon the normal functioning of the weapon, and furthermore, adding to these facts that the bolt is instinctively freed when lo-ading'the gun; it will be appreciated that this mechanism is an ideal means of eliminating the dangers previously referred to, and constitutes a technicalimprovement that definitely solves a long standing problem.

Having now particularly described and'ascertained the nature of the present invention and thema'nnerof its practical performance, I' declare that What I claim is:

Inanautomatic firearm, a housing,- a bolt slidable.in"said housing; said'housing-having a l'o'cking'lateral groove at the forward position of 'fsaid'bolt, a handle attached to 'said bolt forprimingthe latter, a bell crank lever pivoted to "said handle through its angle adjacent'said housing'gsaid bell crank lever having a later'ally" enlarged arm 'of" comparatively small mass "extending". rearwardly parallel to saidhousing in non-locking position, movable into, said housing groove to lock the bolt 25 Number in its forward position, said bell crank lever having a second arm at right angles to said first mentioned arm extending away from said housing, said second arm being of comparatively great 5 mass, and a yieldable pin carried by said second arm of said bell crank lever and engaging said handle to urge said first mentioned laterally enlarged arm into locking engagement mi-said housing groove to prevent accidental release of said 10 lever during non-automatic firing of the weapon, the momentum of the comparatively great mass of said-second-beli, crank lever arm overcoming the urging of said yieldable pin at, its forward position during automatic firing of the weapon whereby the bolt is slidable back and forth with- *'Thefollowingreferences are of=-record in the file of this patent:

t UNITED STATES PATENTS y Name Date 129L689 Sheppard Jan. 14, 1919 "1,574,770 Frommer Mar. 2,' 1926 a FOREIGN PATENTS Number Country Date 32 519 Australia Apr. 10, 1908 

